Probability based design of punching shear resistance of column to slab connections

Abstract

The paper analyzes the dependence of punching shear strength reliability index β, calculated according to EN 1992-1-1:2004 (2004) and STR 2.05.05:2005 (2005) in reinforced concrete floor slab-to-column joint on the values of random factors. The paper deals with theoretical research of the influence of independent random variables, such us the value of the characteristic compressive strength f_ck of concrete, the area A_s of the longitudinal reinforcement, effective cross-section depth d and the ratio of the self-weight and the effective load on the value of the reliability index β. The paper presents experimental results of reinforced concrete slabs with different longitudinal reinforcement ratio ρ subjected to a concentrated load. I t was determined that when the effective load makes around 50% of the construction self-weight load, i.e. G_k /Q_k = 2 and when minimal variation coefficient estimates are taken (for concrete strength δf_c = 0.1, for effective depth δd = 0,1 and for the area of longitudinal reinforcement cross-section δA_s = 0.05 or δA_s = 0.075 and when G_k = Q_k i.e. G_k /Q_k = 1 where δf_c = 0.1, δd = 0.1 and δA_s = 0.05) the reliability index β of the analyzed slabs calculated according to EN 1992-1-1:2004 (2004) as well as β calculated according to STR 2.05.05:2005 (2005), is bigger than EN 1990:2002 (2002) recommendation for the minimum value of reliability index – 3.8 for RC2 construction reliability class ultimate. In other cases the reliability index β is close to 3.8 or much smaller than 3.8.

Keyword : punching shear strength of reinforced concrete slabs, critical perimeter, longitudinal reinforcement ratio ρ, reliability index β, coefficient of variation